The goals of this study are to elucidate the bio behavioral determinants that govern the structure and dynamics of the microbiome of African American (AA) women during pregnancy and to investigate whether microbiome composition is associated with PTB. The proposed study will contribute to a bio psychosocial understanding of within-race risk for PTB, providing insight into important risk and protective factors relevant to AA women who disproportionately experience PTB compared to any other US population. Our research is consistent with frameworks for eliminating racial disparities, which recognize the importance of studying potential risk factors within-race as a vital first step, and is congruent with the National Institute of Nursing Research goal of promoting and improving the health of individuals, families, and communities across the lifespan in a variety of clinical settings and within diverse populations. The study will prospectively enroll a socioeconomically diverse cohort of H 960 pregnant AA women and follow them through delivery, collecting data at three time points: twice via direct participant contact during prenatal care appointments (at 10-14 and 26-30 weeks' gestation), and once via review of the medical records from the delivery hospitalization. Using a nested case-control approach, we will designate as cases all women who experience PTB (an estimated 125 cases); an equal number of controls will be selected from among those who deliver a term infant. Using this study design we will: (1) Characterize the vaginal, oral, and gut microbiome during early and later pregnancy; (2) Examine whether bio behavioral factors linked with PTB - including biological indicators and experiences of stress, nutritional status, and health behaviors - influence the composition of the microbiome; (3) Determine whether the composition of the vaginal, oral, and gut microbiome in early and/or later pregnancy is associated with PTB; and (4) Investigate whether symptom patterns are associated with microbiomic milieu that increase the risk of PTB among AA women. The success of this research is supported by several factors. First, we have assembled a multidisciplinary collaboration of clinicians and basic and translational scientists representing expertise in infectious disease, obstetrics-gynecology, nutrition, genetics and epigenetics, stress physiology, epidemiology and informatics under the leadership of a nurse-scientist. Second, we have the support of the Atlanta Clinical and Translational Science Institute (CTSA award # NIH UL1TR000454); Emory's Interdisciplinary Training for Nurse Scientists Award (T32 NR012715), Emory's Reproductive and Perinatal Epidemiology Fellowship Award, and the Emory Integrated Genomics Core Laboratory. Third, Atlanta is home to AA women of broad SES, many of whom are served by Emory's affiliated delivery hospitals, enabling us to sample a diverse group of AA women, allowing for sufficient variation in the bio behavioral determinants under study to distinguish their independent and interactive effects on the microbiome and, ultimately, on the risk of PTB.